This invention relates to an image projection system for synthesizing, on a screen, images projected from a plurality of projectors to thereby obtain a very fine image.
In the conventional case of representation directed to a great number of people, an over head projector or a slide projector has been used.
In accordance with the proliferation of personal computers and the replenishment of application software, a representation system as a combination of a personal computer and a projection display (hereinafter referred to simply as a "projector") has come to be employed. This system is characterized in that it is not necessary to print, on an OHP sheet, an image or a manuscript created on the screen of the personal computer, or to photograph such an image or a manuscript using a slide film. In the case of a natural image, in particular, the system is characterized in that the colors of the image which are viewed in an image-creating stage can be reproduced without degradation. A projector of this type mainly employs a liquid crystal panel which is lighter and can be installed in an easier manner than the conventional CRT (Cathode Ray Tube) display monitor.
Referring to FIG. 23, an example of a representation system as a combination of a personal computer and a liquid crystal projector will be described.
In FIG. 23, image/manuscript data created on the screen of a personal computer 201 is output from the computer to a processing control section 206 incorporated in a liquid crystal projector 202, through a monitor output terminal incorporated in the computer. The processing control section 206 of the liquid crystal projector 202, in turn, processes the input image data and then outputs it to a liquid crystal panel (LCP) 204. The liquid crystal panel 204 displays an image corresponding to the input image data. Light emitted from a light source 203 is projected onto a screen 208 via a projection lens 207, after the transmissivity of the light is determined on the basis of the gradation of the image displayed on the liquid crystal panel 204.
The resolution of the image projected from the liquid crystal projector 202 is, however, determined on the basis of the number of pixels incorporated in the liquid crystal panel. Although a projector is now available that can receive an image signal of a higher resolution than that of the liquid crystal panel, it is adapted to thin original image data to make the data comply with the number of pixels of the liquid crystal panel, which means that the projector cannot reflect the resolution of the original image.
Moreover, there is also a projector which displays part of an original image and scrolls to make the overall image appear. This projector is, however, disadvantageous in that it cannot show the overall image at one time. To overcome this disadvantage and to obtain a finer projection image, it is necessary to increase the number of pixels incorporated in the liquid crystal panel of the projector. Such a very fine liquid crystal projector is extremely expensive, and hence is not applicable to general use.
Furthermore, when a liquid crystal panel of a high resolution is used, the load upon a process controller incorporated in the projector system will increase, and this panel requires a large display area. Accordingly, the efficiency of use of source light will decrease thereby darkening the projected image.
In addition, to project an accurate image, it is necessary to accurately horizontally dispose the main body of the projector, or to align the main body with the screen. If the projector is not accurately disposed, the projected image may well be angularly displaced, or be "swung and tilted". Also, Japanese Patent Application KOKAI No. 2-306782 discloses a technique for inserting a pre-prepared image (insertion image) into an image photographed by a TV camera. More specifically, the insertion image is inserted into the photographed image by being artificially swung and tilted in a direction in which the camera is situated (this processing is called "perspective transformation"). Supposing that the insertion image is expressed by the (x, y) coordinates and the photographed image is expressed by the (X, Y) coordinates, the primary perspective transformation is given by the following equations (1): EQU X=m.multidot.(d.multidot.x+e.multidot.y+f)/(a.multidot.x+b.multidot.y+c) EQU Y=m.multidot.(g.multidot.x+h.multidot.y+i)/(a.multidot.x+b.multidot.y+c) (1)
Application of this technique to an image projected by the projector, however, requires means for detecting the projection direction of the projector.